Author Topic: Where should the PVR be installed  (Read 1841 times)

Marper

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Where should the PVR be installed
« on: January 06, 2008, 04:21:56 am »
Hi,

Thanks to all of the help on this forum I've been able to get to my next step. 

Should the PVR 150 card be installed and configured on the Core

OR

Should each MD have a card ?

Thanks in advance

Zaerc

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Re: Where should the PVR be installed
« Reply #1 on: January 06, 2008, 04:53:41 am »
Whatever suits your needs, you could do either, or both.
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Marper

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Re: Where should the PVR be installed
« Reply #2 on: January 06, 2008, 05:34:13 am »
Thanks for the response.

If I load the Core with the PVR's I should be able to watch TV on any system ?

Marper

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Re: Where should the PVR be installed
« Reply #3 on: January 06, 2008, 07:21:43 am »
Thanks - I was more concerned about performance and whether or not it would make much of a difference if all of my PVR's were on the core or MD.  Now that I've got my network settings set and proper, it works like a charm.


totallymaxed

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Re: Where should the PVR be installed
« Reply #4 on: January 06, 2008, 03:11:42 pm »
Thanks - I was more concerned about performance and whether or not it would make much of a difference if all of my PVR's were on the core or MD.  Now that I've got my network settings set and proper, it works like a charm.

I'm not sure how MythTV & vdr compare in terms of system overhead when recording off-air/streaming recordings but we have all our DVB cards located in the Core with vdr managing/scheduling/streaming centrally. Looking at my home LinuxMCE 0704 based core right now I see it is streaming a Live TV picture to its Hybrid Orbiter & recording 3 other channels currently and the CPU load is hovering around 5-7% (running UI2 + Overlay on a i945 with 2.8Ghz P4 & 512mb RAM)
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smiler3k

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Re: Where should the PVR be installed
« Reply #5 on: January 06, 2008, 10:11:05 pm »
Another question on the subject if i install a tuner on an md where will it record to. Will it record on to the core or is there an option to record on to a local disk.

ddamron

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Re: Where should the PVR be installed
« Reply #6 on: January 06, 2008, 10:13:45 pm »
It will record to wherever you tell it to.  If you have a HD on your MD, that's best.. but you can also record it to another 'share' located elsewhere.

HTH,

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colinjones

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Re: Where should the PVR be installed
« Reply #7 on: January 06, 2008, 11:35:44 pm »
Thanks - I was more concerned about performance and whether or not it would make much of a difference if all of my PVR's were on the core or MD.  Now that I've got my network settings set and proper, it works like a charm.

I'm not sure how MythTV & vdr compare in terms of system overhead when recording off-air/streaming recordings but we have all our DVB cards located in the Core with vdr managing/scheduling/streaming centrally. Looking at my home LinuxMCE 0704 based core right now I see it is streaming a Live TV picture to its Hybrid Orbiter & recording 3 other channels currently and the CPU load is hovering around 5-7% (running UI2 + Overlay on a i945 with 2.8Ghz P4 & 512mb RAM)

Ahhh, but are you cheating Andrew? Are those 3 channels all mux'd on the same channel or are they genuinely different channels with different tuners? :) i know you have said before that the UK uses a lot of muxing ;)

ddamron

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Re: Where should the PVR be installed
« Reply #8 on: January 07, 2008, 12:55:37 am »
I record from 2 seperate tuners with no problem...
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RichardP

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Re: Where should the PVR be installed
« Reply #9 on: January 07, 2008, 12:06:53 pm »
Ahhh, but are you cheating Andrew? Are those 3 channels all mux'd on the same channel or are they genuinely different channels with different tuners? :) i know you have said before that the UK uses a lot of muxing ;)

Does it make a difference? Will recording 2 channels all on the same mux place less strain on the system than recording 2 channels from 2 seperate cards? And while I'm asking the question, will 2 seperate cards place a different load on the system than a single card with dual tuners?
Best Regards,
Richard

ddamron

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Re: Where should the PVR be installed
« Reply #10 on: January 07, 2008, 01:34:40 pm »
Think of a MUX as a whole bunch of channels.. then there's a FILTER that allows through ONLY the channel you want to record.. it's basically streamed to disk..

When you have 2 channels on the same mux, the only difference is the FILTER (it's opened up to let both channels through) and both streams are saved...
Doing this adds minimal load.

With 2 Tuners, there IS more overhead, as your now dealing with 2 MUXs and 2 FILTERs
Doing this, doubles the load (of the tuner, that is)
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totallymaxed

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Re: Where should the PVR be installed
« Reply #11 on: January 07, 2008, 03:03:01 pm »
Thanks - I was more concerned about performance and whether or not it would make much of a difference if all of my PVR's were on the core or MD.  Now that I've got my network settings set and proper, it works like a charm.

I'm not sure how MythTV & vdr compare in terms of system overhead when recording off-air/streaming recordings but we have all our DVB cards located in the Core with vdr managing/scheduling/streaming centrally. Looking at my home LinuxMCE 0704 based core right now I see it is streaming a Live TV picture to its Hybrid Orbiter & recording 3 other channels currently and the CPU load is hovering around 5-7% (running UI2 + Overlay on a i945 with 2.8Ghz P4 & 512mb RAM)

Ahhh, but are you cheating Andrew? Are those 3 channels all mux'd on the same channel or are they genuinely different channels with different tuners? :) i know you have said before that the UK uses a lot of muxing ;)

I think from memory when I posted that that the recordings were across two different MUX's and I'm not sure what MUX the Live TV picture was on. However I have just done some quick and dirty tests here at the office on one of our AMD64 4400 0710 Cores with 12 recordings running across 4 MUX's we get about a 12% CPU usage.

The DVB-T system transmits a bundle of 'channels' on a given frequency - this is called a Multiplex or MUX (with DVB-S these bundles are called 'Bouquets' for some reason... but the meaning is the same). For DVB-T here in the UK there are 6 national MUX's and each MUX holds between 8 & 14 'channels' of TV and Radio. VDR allocates a DVB Tuner to a given MUX on request and supports the capability to deliver any of the channels available from that MUX concurrently without needing a separate tuner per channel. The only limitation is your Cores ability to sustain the workload. In testing and in real life everyday usage we see no problems playing a DVD or ripped DVD at the Hybrid while recording/streaming multiple TV channels. In fact that is the 'normal' mode my home core is in most of time... and my home Core is not a top end MB/Processor and it only has 512MB RAM
Andy Herron,
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totallymaxed

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Re: Where should the PVR be installed
« Reply #12 on: January 07, 2008, 04:16:02 pm »
Ahhh, but are you cheating Andrew? Are those 3 channels all mux'd on the same channel or are they genuinely different channels with different tuners? :) i know you have said before that the UK uses a lot of muxing ;)

Does it make a difference? Will recording 2 channels all on the same mux place less strain on the system than recording 2 channels from 2 seperate cards? And while I'm asking the question, will 2 seperate cards place a different load on the system than a single card with dual tuners?

Well in 'real life' usage I dont think it does make that much difference whether the channels are from the same MUX or two different ones or at least its not measurable by me.
Andy Herron,
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colinjones

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Re: Where should the PVR be installed
« Reply #13 on: January 07, 2008, 09:50:52 pm »
Sorry guys, I was only joking around. The load is, as Dan said, on the tuner - well the decompression chip, not the CPU. So more channels, whether on the same mux or others won't effect the CPU. Actually recording it is just streaming the encoded (not decoded) transport stream to disk, and even in the most extreme case DVB-T only supports upto 20Mb/s over an entire mux (from memory). So in totallymaxed case in the UK, this is a max of 6x20 - 15MB/s which even the slowest of disks can handly, it is not likely to present any real load to the CPU! Of course if many of these streams are being sent over your network to MDs, then it would present an increasing load on the network..

Totallymaxed - when you have upto 14 channels, unless a lot were radio, I can't imagine that the TV quality would be too great. In AU most SD channels are transmitted between 5-6Mb/s and the HD channels between 9-12Mb/s... what is your impression of the quality of TV when there are a lot on the same mux?

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Re: Where should the PVR be installed
« Reply #14 on: January 08, 2008, 12:15:45 am »
While we are filling in details here is the US approach-
Broadcast (ATSC) is a 20 Mbps stream that can have up to 5 program channels or as little as one. All owned by the same station. All MPEG2. A good HD broadcast (PBS or major sports event) will use most or all of the band. But the stations dynamically adjust to suit their revenue needs.
Cable is a 40MBps stream that can have 10 stations on it. The two system are not RF compatible. And a lot of the cable streams are encrypted.
The same program on broadcast and cable will look considerably better on broadcast. The cable guys recompress the stream to squeeze it.
I don't know as much about the satellite standards and those are changing but I do know that they dynamically change bandwidth and even frequency all the time.

I can record two programs on different streams from the HDHomeRun in HD with no problems. However it strips the streams in hardware.